CVE-2021-20177: Linux Kernel

Medium severity, CVSS 4.4. EPSS: 0.3% chance of exploitation in the next 30 days.

A flaw was found in the Linux kernel's implementation of string matching within a packet. A privileged user (with root or CAP_NET_ADMIN) when inserting iptables rules could insert a rule which can panic the system. Kernel before kernel 5.5-rc1 is affected.

Affected products

• Linux Linux Kernel: up to and including 5.4.9

Published 2021-05-26. Last modified 2026-06-17.